Neopentane is a unique nonpolar hydrocarbon molecule that has found industrial use in the form of an inert condensing agent for gas-phase reactions. See, for instance, U.S. Pat. No. 6,262,192. Other potential industrial uses for neopentane include use as a heat removal agent, a blowing agent, and a gasoline blend component due to its relatively high octane numbers. For instance, neopentane has a Research Octane Number (RON) of 85.5 and a Motor Octane Number (MON) of 80.2.
Many conventional processes for producing neopentane have proven unsatisfactory for application on a commercial scale. For example, typical existing processes for synthesizing neopentane utilize stoichiometric reactions of t-butylchloride and a Grignard reagent, methyl aluminum dichloride, dimethyl aluminum chloride, or trimethyl aluminum. See, for instance, U.S. Pat. No. 3,585,252. Such stoichiometric reactions generate large amounts of metal halides and are difficult to scale up to produce neopentane at commercial quantities. Likewise, though neopentane may be synthesized by hydrogenation of neopentanoic acid under high pressure and at high temperature, e.g., as described in U.S. Pat. No. 4,593,147, such processes are expensive due to the neopentanoic acid feedstock and suffer from a combination of demanding reaction conditions and low selectivity.
Other proposed processes for producing neopentane involve demethylation of higher carbon-number branched paraffins. For example, U.S. Pat. Nos. 4,940,829 and 2,422,675 each relate to the preparation of neopentane via catalytic demethylation of neohexane. However, these higher carbon-number branched paraffins are not readily available in high concentrations suitable as feedstock that could be utilized on a commercial scale.
Alternatively, a process for producing neopentane by hydrogenating an isobutylene polymer and selectively cracking the hydrogenation product is described in U.S. Pat. No. 2,394,743. However, in addition to producing neopentane, this process also produces large amounts of heavier hydrocarbon components.
The production of neopentane by processes that include the demethylation of higher carbon-number hydrocarbons have recently be disclosed in related applications. For instance, WO 2018/044591 discloses a process that includes dimerizing isobutylene to produce diisobutylene, hydrogenating the diisobutylene to yield isooctane, and demethylating the diisobutylene to produce neopentane. Further, WO 2018/044592 discloses a process that includes isomerizing C6 and/or C7 paraffins to produce neohexane and/or neoheptane and demethylating the neohexane and/or neoheptane to produce neopentane. Further still, WO 2018/044596 discloses a process that includes contacting isobutane and butylene under alkylation conditions to produce isooctane and demethylating the isooctane to produce neopentane. Each of these processes is reliant upon a suitable catalyst for the demethylation of the higher carbon-number hydrocarbons to produce neopentane. However, demethylation of the higher carbon-number hydrocarbons to produce neopentane is highly exothermic.
Thus, there is a need for temperature control of the demethylation process used to produce neopentane. Effective temperature control of the demethylation of the higher carbon-number hydrocarbons would allow processes such that those described above to more economically produce neopentane in commercial quantities.
Other references of interest include: “The Preparation and Activity for Alkane Reactions of Aerosil-Supported Rhodium-Copper Clusters,” Clarke et al., Journal of Catalysis, vol. 111, pp. 374-82 (1988); “Selective Demethylation of Paraffin Hydrocarbons: Preparation of Triptane and Neopentane,” Haensel et al., Industrial and Engineering Chemistry, vol. 39, pp. 853-57 (1947); “Skeletal Reactions of Hydrocarbons over Supported Iridium-Gold Catalysts,” Foger et al., Journal of Catalysis, vol. 64, pp. 448-63 (1980); “Reactions of 2,2-Dimethylbutane on Iridium: The Role of Surface Carbonaceous Layers and Metal Particle Size,” Vogelzang et al., Journal of Catalysis, vol. 111, pp. 77-87 (1988); “Hydrogenolysis of 2,2-Dimethylbutane and n-Hexane over Supported Ruthenium, Nickel, Cobalt, and Iron,” Machiels et al., Journal of Catalysis, vol. 58, pp. 268-75 (1979); “Hydrogenolysis of Saturated Hydrocarbons: Influence of Hydrocarbon Structures on the Activity and Selectivity of Nickel on Silica,” Leclercq et al., Journal of Catalysis, vol. 99, pp. 1-11; GB 574694; U.S. Pat. Nos. 2,422,670; 2,436,923; “STRATCO Effluent Refrigerated H2SO4 Alkylation Process,” in Handbook of Petroleum Refining Processes, Third Edition, Graves, ch. 1.2 (2004); and “UOP Alkylene™ Process for Motor Fuel,” in Handbook of Petroleum Refining Processes, Third Edition, Roeseler, ch. 1.3 (2004); and “UOP HF Alkylation Technology,” in Handbook of Petroleum Refining Processes, Third Edition, Himes et al., ch. 1.2 (2004).